- Email: [email protected]
Runaway atrioventricular sequential pacemaker after radiation therapy
CASE REPORTS
Runaway Atrioventricular Sequential Pacemaker after Radiation Therapy
RICHARD W. LEE, M.D. SHOEI K. HUANG, M.D. EILEEN MECHLING, R.N. ION BAZGAN, M.D. Tucson, Arizona
Pacemaker malfunction manifested as a runaway circuitry occurred in two patients after they received radiation therapy for treatment of carcinoma. Both pacemakers were programmable atrioventricular sequential units (WI) with complementary metal oxide semiconductor circuitry. One pacemaker was directly in the radiation field, whereas the other was not directly within the radiation port. Thus, direct irradiation of an implanted pacemaker should be avoided. It is advisable that a pacemaker be shielded even when the pacemaker is not in the direct field of radiation. The number of dual-chamber pacemakers implanted in the United States has steadily increased each year in the past few years. At the same time, radiation therapy has expanded its curative and palliative role in the field of oncology. Therefore, physicians may be likely to encounter patients with pacemakers who require radiation therapy. Previously, our colleagues repotted the first case [I] of radiation therapy-induced damage to an atrioventricular sequential (DVI) pacemaker, manifested as pacemaker runaway. Since then, we have seen another patient with the same problem. In addition, two other cases have been reported [2,3]. This problem of radiation-induced damage is important, since it may be avoided by knowledge of this complication, and because pacemaker runaway due to radiation can cause rapid tachycardia with potentially lethal consequences. Therefore, we wish to report the two cases personally observed and discuss the effects of radiation on the performance of the pulse generator. CASE REPORTS
From the Section of Cardiology, Department of Internal Medicine, University Medical Center, University of Arizona, Tucson, Arizona. Requests for reprints should be addressed to Dr. Shoei K. Huang, Section of Cardiology, University of Arizona Medical Center, Tucson, Arizona 85724. Manuscript submitted June 5, 1985, and accepted July 23, 1985.
Patlent 1. A 46-year-old white woman with rheumatic heart disease had aortic and mitral valve replacement in February 1981. Complete heart block developed during surgery, and an epicardial atrioventricular sequential pacemaker (DVI) was implanted in an abdominal pocket in the right upper quadrant. The pacemaker, an Intermedics model 259-O 1, functioned well. The patient had no further complications postoperatively. In December 1981, the patient was found to have uterine carcinoma with metastasis. She underwent hysterectomy followed by radiation therapy at a local hospital. From December 21, 1981, to January 25, 1982, she received radiation therapy to the right hip and the lumbar spine. A total of 4,500 rads at 180 rads per session was delivered using a linear accelerator. The pacemaker continued to function well, and a pacemaker check in June 1983 showed no evidence of malfunction. From July 22, 1983, to August 22, 1983, she received a second portion of radiation therapy to the midabdominal area. A total of 3,960 rads was given in 22 treatments. The large-scale integration chip of the pulse generator was outside the radiation port but was immediately adjacent to it.
November
1996
The American
Journal
of Medicine
Volume
81
663
PACEMAKER
( III
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
25mmhec
I
Figure 1. Patient 1. Top, electrocardiographic lead ill at 50 mm per second showing atrial runaway at a rate of 300 per minute and a ventricular rate of 104 per minute of an atribventricular sequential pacemaker (Intermedics model 259-O 1). Bottom, electrocardiographic lead ill at 25 mm per second with application of magnet showing total inhibition of atrial output and a fixed ventricular rate of 104 per minute. The fourth beat is a fusion beat: a = atrial spikes; v = ventricular spikes.
On September 1, 1983, the patient presented to our clinic with complaints of fatigue and dyspnea on exertion for two weeks. Electrocardiography showed that the atrium was being paced at 300 beats per minute (Figure 1, top). There were ventricular spikes at 103 beats per minute. With application of the magnet over the pulse generator, the atrial output was inhibited, and the ventricle was firing at a fixed rate of 120 beats per minute. (Figure 1, bottom). For this pacemaker model, application of the magnet should result in atrioventricular pacing at a fixed rate of 90 beats per minute. The pacemaker could not be programmed. The pacemaker was replaced immediately, and the patient’s symptoms were relieved. Analysis of the removed pulse generator by Intermedics indicated that the circuitry damage was consistent with exposure to ionizing radiation. Patient 2. An 80-year-old white woman received a ventricular demand pacemaker in 198 1 for tachycardia-bradycardia syndrome. The pacemaker syndrome, manifested by fatigue and dizziness, developed, and the original pacemaker was replaced with a programmable atrioventricular sequential pacemaker (DVI), an Intermedics model 259-01. The pacemaker was implanted in the right intraclavicular area. Shortly thereafter, infiltrating ductal carcinoma of the right breast was diagnosed. Radiation therapy was started
884
November 1986
The American Journal of Medicine
Ill
25 mm/see
Figure 2. Patient 2. Top, electrocardiographic lead V, at 50 mm per second showing atrial runaway at a rate of 300 per minute and ventricular rate at 103 per minute of an atrioventricular sequential pacemaker (Intermedics model 259-O 7). Bottom, electrocardiographic lead Ill at 25 mm per second with application of magnet. There is total inhibition of both atrial and ventricular outputs. The underlying rhythm is atrial flutter; a = atrial spikes; v = ventricular spikes.
after right simple mastectomy. This was delivered by a linear accelerator through five ports, one port encompassing the area occupied by the pacemaker. At a dose of 3,000 to 3,600 rads, pacemaker malfunction was noted. Electrocardiography showed that the atrial pacemaker was firing at 300 beats per minute (Figure 2, top). The ventricular spike was firing at 104 per minute. With application of the magnet, all pacemaker activity was inhibited, and electrocardiography showed atrial flutter (Figure 2, bottom) that was not present on the previous electrocardiograms. The pacemaker was immediately replaced. Analysis of the removed generator showed that there was damage to the large-scale integrated circuit. This case was previously reported [ 11.
COMMENTS Most implanted pacemakers in existence today are of the ventricular demand type (VVI). However, increasing numbers of pacemakers of the atrioventricular sequential type (DVI) and universal pacemakers (DDD) are being implanted. These units are being constructed with circuitry that is more susceptible to damage from ionizing radiation. Although there is little doubt that radiation doses used for
Volume 81
I
PACEMAKER
diagnostic purposes do not affect cardiac pacemakers either immediately or in small cumulative doses [4], the reports of the effects of radiation on the pacemakers in patients receiving radiation therapy have been contradictory [I ,2,5-g]. Prior to 1978, reports in the literature were reassuring that radiation therapy would not damage pacemaker generators. In 1969, Hildner et al [5] reported that pacemaker function was unaffected in a patient who received radiation for bronchial carcinoma. In addition, they irradiated two Cordis pacemakers, one an atrial synchronized and the other a ventricular demand pacemaker, with 4,600 and 10,000 rads, respectively. These doses did not result in malfunction of the pacemakers. In 1972, Eipper and Laufenberg [6] reported similar findings. In 1975, Walz et al [7] subjected four different types of demand pacemakers to in vitro irradiation with six different radiation therapy devices, including linear accelerations, betatrons, radioactive cobalt, and radiographic equipment. Cumulative doses of up to 30,000 rads were given. They found only minimal changes in pacemaker function consisting of occasional dropped beats, which were attributed to the effects of ancillary equipment. There were no physical changes affecting the battery or electronics of the pacemaker. In 1978, Marbach et al [8] exposed four demand pacemakers to the different electromagnetic fields of betatrons and linear accelerators. In addition, cobalt 60, which has no electromagnetic field, was also used. Their conclusions were that betatrons should not be used in patients with pacemakers and that linear accelerators should be used with extreme caution. They found no pacemaker malfunction with cobalt 60 radiation of less than 7,000 rads, but pacemakers with complementary metal oxide semiconductor (CMOS) circuitry showed a permanent 10 percent decrease in pulse rate after exposure of 7,000 to 9,000 rads. One pacemaker had total failure after 12,000 rads. In 1982, Adamet et al [9] using 10 MeV radiation from a linear accelerator, irradiated 12 demand nonprogrammable and 13 programmable pacemakers up to a total dose of 7,000 rads in divided fractions of 1,000 rads. They found no malfunctions in the nonprogrammable pacemakers but reported sudden output failure in nine of 13 programmable pacemakers. They concluded that irradiation of programmable pacemakers should be avoided. Thus, the iiterature suggests that the older nonprogrammable pacemakers are relatively resistant to radiation damage, whereas the advanced programmable units, especially ones involving complementary metal oxide semiconductor circuitry, are more liable to malfunction after irradiation. Since our initial report in 1982 [ 11, there have been two additional clinical cases [2,3] of pacemaker malfunction after radiation therapy. In one report, [2] the pacemaker’s sensing mechanism malfunctioned after 6,300 rads was delivered to the thoracic area for carcinoma of the mid-
November
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
esophagus. Attempts at external reprogramming failed, and the pacemaker was replaced. An estimated 1,500 rads was delivered to the port encompassing the pacemaker. The type and model of the pacemaker were not given, but malfunction included a change in sensitivity and pulse interval. In the other report [3], pacemaker malfunction occurred after 2,080 rads was given for bronchogenie carcinoma to a port including part of the pacemaker. Of note is that scattered radiation of about 127 rads in an earlier course of therapy produced no malfunction. The pacemaker was an Intermedics model 259-01 atrioventricular sequential programmable pacemaker (DVI). The mode of failure was atrial runaway with an accelerated ventricular pulse rate. One of our patients (Patient 2) received radiation directly to the pacemaker. The amount delivered, 3,000 to 3,600 rads, is within the range of radiation given in the other reported cases. In our other patient, the pacemaker unit was abutting the outlines of the port and the largescale integration chip was outside the immediate field and received only scattered radiation. However, direct radiation of a small portion of the pacemaker cannot be definitely excluded. Analysis of the two electrocardiographic tracings indicated a similar mode of failure. There was damage to both atrial and ventricular circuits. There was atrial runaway at 300 beats per minute. The ventricular pulse interval was slower because of a built-in circuit that prevents ventricular runaway. With atrioventricular sequential pacemakers (DVI), atrial runaway at a rapid pacing rate can occur with variable and slower (protected) ventricular pacing. Our experience and that of others indicate that the newer advanced programmable pacemakers with complementary metal oxide semiconductor circuitry components are susceptible to damage by direct irradiation. It is not clear whether or not they can be damaged by scattered radiation, and this needs further investigation. The reason for the apparent enhanced susceptibility to radiation of the newer pacemakers has not been defined. Older pacemakers used bipolar semiconductors for their circuitry, whereas many newer units employ complementary metal oxide semiconductor circuitry for large-scale integration of functions. These circuits are known to be reliable and energy-efficient. However, the older circuits were radioresistant, whereas damage to complementary metal oxide semiconductor circuitry devices has been reported to occur at radiation doses as low as 1,000 rads [ 10,111. Failure of memory circuits has been reported at 5,000 to 15,000 rads [10,11]. Radiation therapy can exert either an ionizing effect alone or an ionizing and electromagnetic effect. Cobalt 60 produces ionizing effects, and betatrons and linear accelerators produce both ionizing and electromagnetic effects. Electromagneticinduced malfunctions are usually transient [8]. They occur when noises and interference patterns are introduced into
1986
The
American
Journal
of Medicine
Volume
81
885
PACEMAKER
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
the pacemaker unit and disappear after cessation of therapy. The electrical field from the beam can cause an erratic output, and the magnetic field can close the reed relay switch in the pacemaker resulting in loss of inhibitory function. Ionizing effects, however, can be cumulative and permanent. When units with complementary metal oxide semiconductor circuitry are exposed to radiation, there is subatomic damage resulting in current leakage and phantom connections between adjacent parts of the circuit. Because of the complexity of the circuit, the mode of failure cannot be accurately predicted [12]. It is of interest though, that both of our cases and the case reported by Quertermonus et al [3] involved similar pacemakers (DVI, Intermedics model 259-01) and resulted in the same kind of failure. It is unknown as yet whether other types of dual-chamber pacemakers from different manufacturers are subject to damage from radiation. In summary, it is important to realize that radiation therapy can produce variable, important malfunctions of the more advanced programmable pacemakers using complementary metal oxide semiconductor circuitry. Phy-
sicians should be aware that the major United States pacemaker manufacturers are now using complementary metal oxide semiconductor circuitry in their advanced pacemakers (DVI and DDD), although the insulation and “housing” of the chips might vary from company to company. When patients with these types of pacemakers require radiation therapy, their units should be shielded if possible. Every attempt should be made to avoid direct irradiation of the pulse generator. If it is not possible to avoid direct irradiation of the unit, consideration should be given to moving the pacemaker to a different site before radiation is given. Electrocardiographic monitoring should be maintained during radiation therapy, and the pacemaker should be tested frequently during and after cessation of therapy if exposure cannot be avoided. ACKNOWLEDGMENT We would like to thank Dr. Frank I. Marcus for review of this manuscript, Mr. Chris Bowman of Intermedics Inc. for his cooperation, and Ms. Laurette Hopper for her secretarial assistance.
REFERENCES 1.
2. 3.
4. 5.
6.
7.
888
Katzenberg CA, Marcus FI, Heusinkveld RS, Mammana RB: Pacemaker failure due to radiation therapy. PACE 1982; 5: 156-159. Pourhamidi AH: Radiation effect on implanted pacemakers. Chest 1983; 84: 499-500. Quertermonus T, Megahy SM, DasGupta DS, Griem ML: Pacemaker failure resulting from radiation damage. Radiology 1983; 148: 257-258. Blamires NG, Myatt J: X-ray effects on pacemaker type circuits. PACE 1982; 5: 151-155. Hildner FJ, Linhart JW, Poole DO: Irradiation of pulmonary tumor with overlying artificial cardiac pacemaker. Radiology 1969; 92: 148-149. Eipper HH, Laufenberg E: Zum Verhalten implantierharer herzschrittmacher wahrend Betatron-Huch volt-Bestrahlung. Strahlentherapie 1972; 143: 644-654. Walz JB, Neder RE, Pastore JO, Littman PH, Johnson R:
November
1986
The
American
Journal
of Medicine
8.
9.
10.
11.
12.
Volume
81
Cardiac pacemakers. Does radiation therapy affect performance? JAMA 1975; 234: 72-73. Marbach JR, Meoz-Mendez RT, Huffman JK, et al: The effects on cardiac pacemakers of ionizing radiation and electromagnetic interference from radiotherapy machines. J Radiat Oncol Biol Phys 1978; 4: 1055-1058. Adamec R, Haefliger JM, Killisch JP, Niedeuer J, Jaquet P: Damaging effect of therapeutic radiation on programmable pacemakers. PACE 1982; 5: 146-150. Matteucci AJ, Schneider MF: Radiation testing complementary metal oxide semiconductor (CMOS) arrays for satellites. IEEE Trans Nucl Sci 1977; 24: 2285-2287. Brucker GJ, Heagerty W: Radiation effects in a CMOS/ SOS/AL-gate D-A converter and on chip diagnostic transistor. IEEE Trans Nucl Sci 1976; 23: 1617-1622. Calfee RF: Therapeutic radiation and pacemakers. PACE 1982; 5: 160-161.
Runaway Atrioventricular Sequential Pacemaker after Radiation Therapy
RICHARD W. LEE, M.D. SHOEI K. HUANG, M.D. EILEEN MECHLING, R.N. ION BAZGAN, M.D. Tucson, Arizona
Pacemaker malfunction manifested as a runaway circuitry occurred in two patients after they received radiation therapy for treatment of carcinoma. Both pacemakers were programmable atrioventricular sequential units (WI) with complementary metal oxide semiconductor circuitry. One pacemaker was directly in the radiation field, whereas the other was not directly within the radiation port. Thus, direct irradiation of an implanted pacemaker should be avoided. It is advisable that a pacemaker be shielded even when the pacemaker is not in the direct field of radiation. The number of dual-chamber pacemakers implanted in the United States has steadily increased each year in the past few years. At the same time, radiation therapy has expanded its curative and palliative role in the field of oncology. Therefore, physicians may be likely to encounter patients with pacemakers who require radiation therapy. Previously, our colleagues repotted the first case [I] of radiation therapy-induced damage to an atrioventricular sequential (DVI) pacemaker, manifested as pacemaker runaway. Since then, we have seen another patient with the same problem. In addition, two other cases have been reported [2,3]. This problem of radiation-induced damage is important, since it may be avoided by knowledge of this complication, and because pacemaker runaway due to radiation can cause rapid tachycardia with potentially lethal consequences. Therefore, we wish to report the two cases personally observed and discuss the effects of radiation on the performance of the pulse generator. CASE REPORTS
From the Section of Cardiology, Department of Internal Medicine, University Medical Center, University of Arizona, Tucson, Arizona. Requests for reprints should be addressed to Dr. Shoei K. Huang, Section of Cardiology, University of Arizona Medical Center, Tucson, Arizona 85724. Manuscript submitted June 5, 1985, and accepted July 23, 1985.
Patlent 1. A 46-year-old white woman with rheumatic heart disease had aortic and mitral valve replacement in February 1981. Complete heart block developed during surgery, and an epicardial atrioventricular sequential pacemaker (DVI) was implanted in an abdominal pocket in the right upper quadrant. The pacemaker, an Intermedics model 259-O 1, functioned well. The patient had no further complications postoperatively. In December 1981, the patient was found to have uterine carcinoma with metastasis. She underwent hysterectomy followed by radiation therapy at a local hospital. From December 21, 1981, to January 25, 1982, she received radiation therapy to the right hip and the lumbar spine. A total of 4,500 rads at 180 rads per session was delivered using a linear accelerator. The pacemaker continued to function well, and a pacemaker check in June 1983 showed no evidence of malfunction. From July 22, 1983, to August 22, 1983, she received a second portion of radiation therapy to the midabdominal area. A total of 3,960 rads was given in 22 treatments. The large-scale integration chip of the pulse generator was outside the radiation port but was immediately adjacent to it.
November
1996
The American
Journal
of Medicine
Volume
81
663
PACEMAKER
( III
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
25mmhec
I
Figure 1. Patient 1. Top, electrocardiographic lead ill at 50 mm per second showing atrial runaway at a rate of 300 per minute and a ventricular rate of 104 per minute of an atribventricular sequential pacemaker (Intermedics model 259-O 1). Bottom, electrocardiographic lead ill at 25 mm per second with application of magnet showing total inhibition of atrial output and a fixed ventricular rate of 104 per minute. The fourth beat is a fusion beat: a = atrial spikes; v = ventricular spikes.
On September 1, 1983, the patient presented to our clinic with complaints of fatigue and dyspnea on exertion for two weeks. Electrocardiography showed that the atrium was being paced at 300 beats per minute (Figure 1, top). There were ventricular spikes at 103 beats per minute. With application of the magnet over the pulse generator, the atrial output was inhibited, and the ventricle was firing at a fixed rate of 120 beats per minute. (Figure 1, bottom). For this pacemaker model, application of the magnet should result in atrioventricular pacing at a fixed rate of 90 beats per minute. The pacemaker could not be programmed. The pacemaker was replaced immediately, and the patient’s symptoms were relieved. Analysis of the removed pulse generator by Intermedics indicated that the circuitry damage was consistent with exposure to ionizing radiation. Patient 2. An 80-year-old white woman received a ventricular demand pacemaker in 198 1 for tachycardia-bradycardia syndrome. The pacemaker syndrome, manifested by fatigue and dizziness, developed, and the original pacemaker was replaced with a programmable atrioventricular sequential pacemaker (DVI), an Intermedics model 259-01. The pacemaker was implanted in the right intraclavicular area. Shortly thereafter, infiltrating ductal carcinoma of the right breast was diagnosed. Radiation therapy was started
884
November 1986
The American Journal of Medicine
Ill
25 mm/see
Figure 2. Patient 2. Top, electrocardiographic lead V, at 50 mm per second showing atrial runaway at a rate of 300 per minute and ventricular rate at 103 per minute of an atrioventricular sequential pacemaker (Intermedics model 259-O 7). Bottom, electrocardiographic lead Ill at 25 mm per second with application of magnet. There is total inhibition of both atrial and ventricular outputs. The underlying rhythm is atrial flutter; a = atrial spikes; v = ventricular spikes.
after right simple mastectomy. This was delivered by a linear accelerator through five ports, one port encompassing the area occupied by the pacemaker. At a dose of 3,000 to 3,600 rads, pacemaker malfunction was noted. Electrocardiography showed that the atrial pacemaker was firing at 300 beats per minute (Figure 2, top). The ventricular spike was firing at 104 per minute. With application of the magnet, all pacemaker activity was inhibited, and electrocardiography showed atrial flutter (Figure 2, bottom) that was not present on the previous electrocardiograms. The pacemaker was immediately replaced. Analysis of the removed generator showed that there was damage to the large-scale integrated circuit. This case was previously reported [ 11.
COMMENTS Most implanted pacemakers in existence today are of the ventricular demand type (VVI). However, increasing numbers of pacemakers of the atrioventricular sequential type (DVI) and universal pacemakers (DDD) are being implanted. These units are being constructed with circuitry that is more susceptible to damage from ionizing radiation. Although there is little doubt that radiation doses used for
Volume 81
I
PACEMAKER
diagnostic purposes do not affect cardiac pacemakers either immediately or in small cumulative doses [4], the reports of the effects of radiation on the pacemakers in patients receiving radiation therapy have been contradictory [I ,2,5-g]. Prior to 1978, reports in the literature were reassuring that radiation therapy would not damage pacemaker generators. In 1969, Hildner et al [5] reported that pacemaker function was unaffected in a patient who received radiation for bronchial carcinoma. In addition, they irradiated two Cordis pacemakers, one an atrial synchronized and the other a ventricular demand pacemaker, with 4,600 and 10,000 rads, respectively. These doses did not result in malfunction of the pacemakers. In 1972, Eipper and Laufenberg [6] reported similar findings. In 1975, Walz et al [7] subjected four different types of demand pacemakers to in vitro irradiation with six different radiation therapy devices, including linear accelerations, betatrons, radioactive cobalt, and radiographic equipment. Cumulative doses of up to 30,000 rads were given. They found only minimal changes in pacemaker function consisting of occasional dropped beats, which were attributed to the effects of ancillary equipment. There were no physical changes affecting the battery or electronics of the pacemaker. In 1978, Marbach et al [8] exposed four demand pacemakers to the different electromagnetic fields of betatrons and linear accelerators. In addition, cobalt 60, which has no electromagnetic field, was also used. Their conclusions were that betatrons should not be used in patients with pacemakers and that linear accelerators should be used with extreme caution. They found no pacemaker malfunction with cobalt 60 radiation of less than 7,000 rads, but pacemakers with complementary metal oxide semiconductor (CMOS) circuitry showed a permanent 10 percent decrease in pulse rate after exposure of 7,000 to 9,000 rads. One pacemaker had total failure after 12,000 rads. In 1982, Adamet et al [9] using 10 MeV radiation from a linear accelerator, irradiated 12 demand nonprogrammable and 13 programmable pacemakers up to a total dose of 7,000 rads in divided fractions of 1,000 rads. They found no malfunctions in the nonprogrammable pacemakers but reported sudden output failure in nine of 13 programmable pacemakers. They concluded that irradiation of programmable pacemakers should be avoided. Thus, the iiterature suggests that the older nonprogrammable pacemakers are relatively resistant to radiation damage, whereas the advanced programmable units, especially ones involving complementary metal oxide semiconductor circuitry, are more liable to malfunction after irradiation. Since our initial report in 1982 [ 11, there have been two additional clinical cases [2,3] of pacemaker malfunction after radiation therapy. In one report, [2] the pacemaker’s sensing mechanism malfunctioned after 6,300 rads was delivered to the thoracic area for carcinoma of the mid-
November
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
esophagus. Attempts at external reprogramming failed, and the pacemaker was replaced. An estimated 1,500 rads was delivered to the port encompassing the pacemaker. The type and model of the pacemaker were not given, but malfunction included a change in sensitivity and pulse interval. In the other report [3], pacemaker malfunction occurred after 2,080 rads was given for bronchogenie carcinoma to a port including part of the pacemaker. Of note is that scattered radiation of about 127 rads in an earlier course of therapy produced no malfunction. The pacemaker was an Intermedics model 259-01 atrioventricular sequential programmable pacemaker (DVI). The mode of failure was atrial runaway with an accelerated ventricular pulse rate. One of our patients (Patient 2) received radiation directly to the pacemaker. The amount delivered, 3,000 to 3,600 rads, is within the range of radiation given in the other reported cases. In our other patient, the pacemaker unit was abutting the outlines of the port and the largescale integration chip was outside the immediate field and received only scattered radiation. However, direct radiation of a small portion of the pacemaker cannot be definitely excluded. Analysis of the two electrocardiographic tracings indicated a similar mode of failure. There was damage to both atrial and ventricular circuits. There was atrial runaway at 300 beats per minute. The ventricular pulse interval was slower because of a built-in circuit that prevents ventricular runaway. With atrioventricular sequential pacemakers (DVI), atrial runaway at a rapid pacing rate can occur with variable and slower (protected) ventricular pacing. Our experience and that of others indicate that the newer advanced programmable pacemakers with complementary metal oxide semiconductor circuitry components are susceptible to damage by direct irradiation. It is not clear whether or not they can be damaged by scattered radiation, and this needs further investigation. The reason for the apparent enhanced susceptibility to radiation of the newer pacemakers has not been defined. Older pacemakers used bipolar semiconductors for their circuitry, whereas many newer units employ complementary metal oxide semiconductor circuitry for large-scale integration of functions. These circuits are known to be reliable and energy-efficient. However, the older circuits were radioresistant, whereas damage to complementary metal oxide semiconductor circuitry devices has been reported to occur at radiation doses as low as 1,000 rads [ 10,111. Failure of memory circuits has been reported at 5,000 to 15,000 rads [10,11]. Radiation therapy can exert either an ionizing effect alone or an ionizing and electromagnetic effect. Cobalt 60 produces ionizing effects, and betatrons and linear accelerators produce both ionizing and electromagnetic effects. Electromagneticinduced malfunctions are usually transient [8]. They occur when noises and interference patterns are introduced into
1986
The
American
Journal
of Medicine
Volume
81
885
PACEMAKER
MALFUNCTION
AFTER
IRRADIATION-LEE
ET AL
the pacemaker unit and disappear after cessation of therapy. The electrical field from the beam can cause an erratic output, and the magnetic field can close the reed relay switch in the pacemaker resulting in loss of inhibitory function. Ionizing effects, however, can be cumulative and permanent. When units with complementary metal oxide semiconductor circuitry are exposed to radiation, there is subatomic damage resulting in current leakage and phantom connections between adjacent parts of the circuit. Because of the complexity of the circuit, the mode of failure cannot be accurately predicted [12]. It is of interest though, that both of our cases and the case reported by Quertermonus et al [3] involved similar pacemakers (DVI, Intermedics model 259-01) and resulted in the same kind of failure. It is unknown as yet whether other types of dual-chamber pacemakers from different manufacturers are subject to damage from radiation. In summary, it is important to realize that radiation therapy can produce variable, important malfunctions of the more advanced programmable pacemakers using complementary metal oxide semiconductor circuitry. Phy-
sicians should be aware that the major United States pacemaker manufacturers are now using complementary metal oxide semiconductor circuitry in their advanced pacemakers (DVI and DDD), although the insulation and “housing” of the chips might vary from company to company. When patients with these types of pacemakers require radiation therapy, their units should be shielded if possible. Every attempt should be made to avoid direct irradiation of the pulse generator. If it is not possible to avoid direct irradiation of the unit, consideration should be given to moving the pacemaker to a different site before radiation is given. Electrocardiographic monitoring should be maintained during radiation therapy, and the pacemaker should be tested frequently during and after cessation of therapy if exposure cannot be avoided. ACKNOWLEDGMENT We would like to thank Dr. Frank I. Marcus for review of this manuscript, Mr. Chris Bowman of Intermedics Inc. for his cooperation, and Ms. Laurette Hopper for her secretarial assistance.
REFERENCES 1.
2. 3.
4. 5.
6.
7.
888
Katzenberg CA, Marcus FI, Heusinkveld RS, Mammana RB: Pacemaker failure due to radiation therapy. PACE 1982; 5: 156-159. Pourhamidi AH: Radiation effect on implanted pacemakers. Chest 1983; 84: 499-500. Quertermonus T, Megahy SM, DasGupta DS, Griem ML: Pacemaker failure resulting from radiation damage. Radiology 1983; 148: 257-258. Blamires NG, Myatt J: X-ray effects on pacemaker type circuits. PACE 1982; 5: 151-155. Hildner FJ, Linhart JW, Poole DO: Irradiation of pulmonary tumor with overlying artificial cardiac pacemaker. Radiology 1969; 92: 148-149. Eipper HH, Laufenberg E: Zum Verhalten implantierharer herzschrittmacher wahrend Betatron-Huch volt-Bestrahlung. Strahlentherapie 1972; 143: 644-654. Walz JB, Neder RE, Pastore JO, Littman PH, Johnson R:
November
1986
The
American
Journal
of Medicine
8.
9.
10.
11.
12.
Volume
81
Cardiac pacemakers. Does radiation therapy affect performance? JAMA 1975; 234: 72-73. Marbach JR, Meoz-Mendez RT, Huffman JK, et al: The effects on cardiac pacemakers of ionizing radiation and electromagnetic interference from radiotherapy machines. J Radiat Oncol Biol Phys 1978; 4: 1055-1058. Adamec R, Haefliger JM, Killisch JP, Niedeuer J, Jaquet P: Damaging effect of therapeutic radiation on programmable pacemakers. PACE 1982; 5: 146-150. Matteucci AJ, Schneider MF: Radiation testing complementary metal oxide semiconductor (CMOS) arrays for satellites. IEEE Trans Nucl Sci 1977; 24: 2285-2287. Brucker GJ, Heagerty W: Radiation effects in a CMOS/ SOS/AL-gate D-A converter and on chip diagnostic transistor. IEEE Trans Nucl Sci 1976; 23: 1617-1622. Calfee RF: Therapeutic radiation and pacemakers. PACE 1982; 5: 160-161.